get rid of most clazy warnings (https://github.com/KDE/clazy)
* range loop use refs
* qcolor ctor with ints
* missing Q_OBJECT macro
* use .constfirst instead of .first
enabled ccache for unix systems for fasterr recompiling
* if ccache is in path we use it now
* reduced minimized file state to one-colored block
* added hover states to file buttons
* show hover state when hovering title bar
* fixed file button use for overview stats snippet
Andreas Stallinger